Planting Trees - 1998

Although the total acreage of subtropical fruit trees is declining in Southern California, growers are replanting declining groves and switching over from old varieties to new.  The future health and production of fruit trees depend on the care given the trees at planting and during the first few years of growth.  Neglect of young trees can cause many to die or be reduced in vigor. 

Subtropicals are best planted in March, April, May or June.  If the orchard is in a cold spot, plant the trees as soon as possible after frost danger has passed to take advantage of the long growing season.  The earlier the planting date, the better established the trees will in the first year.

Prior to planting prepare the area to be planted.  Any preplant amendments, pH adjustment or subsurface drainage should be performed before holes are prepared.  Any ripping to break up soil compaction or layered soils should be done, if necessary.  The underground portion of the irrigation system should be installed.  In the case of avocado, mounds or berms should be created on relatively flat land to improve soil drainage and aeration.

The planting hole should be the same depth, or slightly shallower than the tree container.  Trees should be planted slightly higher than the surrounding soil surface so that once settling occurs, no part of the stem is underground.  It should be wide enough to accommodate the roots of a bare root tree or provide enough space to remove the plastic bag in container-grown trees.  Usually 6 to 8 inches wider than the diameter of the root ball is adequate so that soil can be tamped around the roots after the tree is placed in the hole. If a soil auger is used for the holes, make sure the sides of the hole have not been slicked.  This can lead to poor water movement and restricted root development.  The irrigation system should be ready to receive the trees at this point.

To plant a container-grown tree, carefully place the container in the hole.  Using a sharp knife, slit the sides of the container and remove it.  Backfill with native soil, tamping as you fill.  Aside from the added cost, use of a commercial planting mix should be avoided.  The textural difference between it and the surrounding soil can often lead to poor soil water movement, creating conditions around the root ball that are too wet or too dry.  Once planted, the tree should be watered soon after.  To make sure the soil around the trees is settled and well soaked, apply a second irrigation the day after planting.

The most important cultural practice, once the trees are planted is irrigation.  Because of the small rooting volume, trees need frequent small amounts of water.  Timing is controlled by climate, but spring weather often means 8 to 10 gallons of water every 5 - 7 days on the root ball.  As roots move into the surrounding soil, less frequent irrigations will be needed.

Fertilization requirements are small for young trees.  A tablespoon per tree of your favorite nitrogen fertilizer every third irrigation should be adequate.  By the second year, 1/8 pound of actual N per tree is suggested and 1/4 pound in years 3 and 4.  By the fifth year, fertilization should be guided by leaf tissue analysis.

Trunk wraps and white latex paints are used to protect young tree stems from sun and cold; they also reduce the amount of suckering.  With some wraps, such as cardboard cylinders, temperatures inside the cylinders may become hot enough to cause stem damage.  Punching holes in all sides of the cylinder can increase air circulation and reduce the problem.

Staking trees is only advisable when trees are top heavy.  In this case often the best option is to head the tree back so that it can support its own weight.  If stakes are used, ties should be made loose so that the tree can move in the wind.  The stakes should be removed as soon as the tree stands free, so that the tree trunk can develop girth.

Weeds and pests need to be controlled.  Use of an herbicide (being especially careful to avoid spray drift onto trunks) or mulching around the base of the tree will reduce weed competition for water and nutrients.  A good control program for gophers, rabbits, voles and squirrels needs to be maintained to avoid these especially harmful pests.

Assuming you have chosen the right cultivar/rootstock combination and the right site with good water and soil, your trees should thrive with this early care.